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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.doris.nereids.trees.expressions.functions.generator;

import org.apache.doris.catalog.FunctionSignature;
import org.apache.doris.nereids.trees.expressions.Expression;
import org.apache.doris.nereids.trees.expressions.functions.AlwaysNullable;
import org.apache.doris.nereids.trees.expressions.literal.StructLiteral;
import org.apache.doris.nereids.trees.expressions.shape.UnaryExpression;
import org.apache.doris.nereids.trees.expressions.visitor.ExpressionVisitor;
import org.apache.doris.nereids.types.JsonType;
import org.apache.doris.nereids.types.StringType;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;

import java.util.List;

/**
 * explode_json_object("{"amory":1, "doris": 2}") generate two column and two lines with:
 *      key column: amory, doris
 *      value column: 1, 2
 */
public class ExplodeJsonObject extends TableGeneratingFunction implements UnaryExpression, AlwaysNullable {

    public static final List<FunctionSignature> SIGNATURES = ImmutableList.of(
            FunctionSignature.ret(StructLiteral.constructStructType(
                    ImmutableList.of(StringType.INSTANCE, JsonType.INSTANCE))).args(JsonType.INSTANCE));

    /**
     * constructor with 1 argument.
     */
    public ExplodeJsonObject(Expression arg) {
        super("explode_json_object", arg);
    }

    /** constructor for withChildren and reuse signature */
    private ExplodeJsonObject(GeneratorFunctionParams functionParams) {
        super(functionParams);
    }

    /**
     * withChildren.
     */
    @Override
    public ExplodeJsonObject withChildren(List<Expression> children) {
        Preconditions.checkArgument(children.size() == 1);
        return new ExplodeJsonObject(getFunctionParams(children));
    }

    @Override
    public List<FunctionSignature> getSignatures() {
        return SIGNATURES;
    }

    @Override
    public <R, C> R accept(ExpressionVisitor<R, C> visitor, C context) {
        return visitor.visitExplodeJsonObject(this, context);
    }
}
